In the field of motor vehicle technology, various solutions are known from the prior art for providing a wheel suspension unit with which driven or non-driven wheels of a motor vehicle can be spring-mounted so as to be rotatable relative to a body.
Many driven wheels of motor vehicles are fixed to a flange part of a hub by bolts, and an end of a driveshaft is wedge-fitted to the hub so that the hub is turned by rotation of the driveshaft in order to rotate the wheel. The hub is rotatably mounted via a wheel bearing or hub bearing in a mounting hole of a stub axle or wheel carrier. The hub bearing has a bearing inner ring and a bearing outer ring, wherein the bearing inner ring is fixedly connected to the wheel hub and the bearing outer ring is fixedly connected to the stub axle or wheel carrier.
Hub bearings of an early development stage have a structure in which the bearing outer ring is connected to the stub axle by press fitting in a mounting hole thereof.
When the stub axle and the wheel bearing or hub bearing are made of materials with widely differing temperature expansion coefficients, as is the case for example when using stub axles or wheel carriers made of aluminum to save weight, the press fit must be greatly over-dimensioned. This can make production of the press fit difficult because one of the components could be deformed on application of the necessary pressing force.
For this reason, KR 20090115601 A and KR 20090115560 A, discussed below, disclose wheel hubs with a hub bearing in which an outer ring of the hub bearing can be connected to the stub axle or wheel carrier by means of threaded bolts. This solution requires a greater installation complexity and entails restrictions in relation to a possible physical arrangement of the hub bearing, stub axle or wheel carrier and brake caliper.
KR 20090115601 A therefore proposes a wheel hub bearing coupling structure of a vehicle, with which a wheel hub bearing can be attached to a wheel carrier. The wheel hub bearing coupling structure comprises an inner threaded part and an outer threaded part. The inner threaded part is formed as a threaded nut element in an inner periphery of a central mounting hole of the wheel carrier. An outer ring of the wheel hub bearing coupling structure is equipped with an outer threaded part for connection to the mounting hole. Balls are provided as a roller bearing between the outer ring and an inner ring of the wheel bearing fixing unit. Mounting takes place by screwing the outer threaded part of the wheel hub bearing coupling structure into the inner threaded part of the mounting hole of the wheel carrier, so that deformation of the wheel bearing can be avoided.
In KR 20090115560 A, a fixing structure for a wheel hub bearing is described with which the contact pressure forces between the wheel hub and wheel hub bearing, or between the wheel hub bearing and the driveshaft, can be adjusted. The wheel hub bearing coupling structure of KR 20090115601 A is changed in relation to the wheel hub bearing fixing structure, in that this comprises a wheel hub bearing with an outer ring and a first and a second inner ring, and a wheel hub on which the wheel hub bearing is mounted. Balls are used as roller bearings between the outer ring and the first and the second inner rings respectively. A screw nut thread is formed on a periphery of an inner face of the second inner ring, and an outer thread adapted to the screw nut thread is formed on a peripheral face of the inner end of the wheel hub.
FIG. 1 shows a diagrammatic depiction of a wheel hub bearing unit 100 of a motor vehicle according to KR 20090115601 A in a sectional side view. The wheel hub bearing unit 100 comprises a wheel hub bearing 101 for mounting a wheel hub, and a wheel carrier 110 with a mounting hole 111. The wheel hub bearing 100 contains an outer ring and an inner ring 103, between which two rows of balls are arranged on the periphery. The outer ring is equipped with an outer thread 102 on its outer peripheral face over its entire axial length. A wall of the mounting hole 111 of the wheel carrier 110 is equipped with an inner thread 112, which corresponds to the outer thread 102 and is provided for mechanical engagement with the outer thread 102. The wheel hub bearing 101 is mounted in the wheel carrier 110 in that the outer ring of the wheel hub bearing 101 is screwed into the inner thread 112 of the mounting hole 111.
In view of the indicated prior art, the area of fixing structures for wheel hub bearings leaves room for improvement.